This multicenter study will validate a panel of serum, imaging, and clinical biomarkers to classify patient outcome early after out-of-hospital pediatric cardiac arrest. Results are expected to have a positive and immediate impact in advancing clinical care and outcomes for these children. This work will provide clinicians, families, and researchers with superior tools to assess the severity of brain injury early after resuscitation in order to know who is at risk of brain injury and may benefit from neuroprotective interventions, to monitor response to these interventions, to plan rehabilitation strategy, and to optimize the design of research studies that test novel interventions to improve neurological outcome after cardiac arrest.